I WAS DRIVING THE SPEED LIMIT AT 40MPH. THE COLLISION MITIGATION BRAKING SYSTEM FIRED ON AN OPEN ROAD CAUSING MY CAR TO STOP ABRUPTLY. THIS CAUSED ME TO GET REAR ENDED BY THE CAR BEHIND ME. THERE WASN'T A CAR IN FRONT OF ME, IT FIRED ERRATICALLY. POLICE REPORT WAS FILED. AFTER TAKING THE CAR TO THE DEALER, THE DEALER HAS INDICATED "THERE IS NOTHING WRONG". EVEN THOUGH THERE WERE WITNESS'S AT THE SCENE AS WELL AS IT CAUSING AN ACCIDENT.